Filter network for radio receivers



June 6, 1939.

R. RECHNITZER 2,161,315

FILTER NETWORK FOR RADIO RECEIVERS Filed Nov. 7, 1956 ms mm 7W5 RES/$74M? CHARACTER/8N6 7 4-T 3 4 T RECE/VER INVENTOR Rl/OUZF fiH'bW/TZER Adm/u ATTORNEY Patented June 6, 1939 UNITED STATES PATENT OFFICE FILTER NETWORK FOR RADIO RECEIVERS tion of Germany Application November 7, 1936, Serial No. 109,614 In Germany November 8, 1935 1 Claim.

The invention concerns a filter network for connecting radio apparatus, in particular a receiver, to the operating potential source. In some cases resistances are used as series elements 5 in the line from the potential source and con- 'sistances and thus a smaller useful potential is available.

The invention proposes, for eliminating these difiiculties, to use as series elements of the filter system or network, series resistances posessing a 5 negative resistance characteristic.

Resistances of this type, which for instance have been put on the market under the name Urdox, change their resistance value with an increasing flow of direct current in that the resistance is lessened. It is possible to insure that the product, I. R., that is the potential drop at the resistance, is practically made independent ofthe size of the load current. Accordingly, the same potential is always impressed on the tubes 25 of the receiver and the above described disturbances are, to say the least, greatly reduced.

The arrangement of resistances of this type with negative resistance characteristic as series elements in filters offers still another advantage. Since they change their resistance according to the current intensity, the filtering is practically reciprocally proportional to the current and thus to the end output. An arrangement is accordingly insured where the residual hum is smaller or larger in proportion to the final output which in addition is very desirable and efficient.

The single figure of the accompanying drawing shows diagrammatically a circuit scheme according to the invention, without the latter being limited thereby. Receiver I is connected with potential source 2 through a filter network consisting of series resistances 3 and by-pass condensers 4. The series resistances have a negative resistance characteristic in accordance with the invention.

What I claim is:

A filter network having input terminals for connection to a source of fluctuating current power supply, and output terminals for connection to radio apparatus, ohmic resistances connected in series in said filter and condensers in parallel across the filter at the terminals of said resistances, said resistances having a negative resistance characteristic such that the voltage supplied to the radio apparatus from across the output terminals of the filter network is maintained substantially constant irrespective of variations in current consumption by said radio apparatus.

RUDOLF RECHNITZER. 

